The present invention relates to an oscillator circuit and to a method for generating an oscillator signal.
Oscillators are playing a key role in integrated circuit design. Almost every digital core needs some sort of clock generator to enable the operation of the circuit. There are many different possibilities to design an oscillator known in the art. The most precise oscillator is built up with quartz. The drawbacks of quartz oscillators, however, include limited temperature range from −40° to 125° C. and that quartz is an expensive external component which cannot be easily integrated, e.g. into the same silicon chip as the rest of the circuit.
Many applications, however, need an extended temperature range which may span −40° to 170° C. Furthermore, external components such as quartz are expensive and lead to rather high production costs. There are some designs known in the art to implement fully integrated CMOS oscillators. Such circuits are often required to combine low temperature drift of output frequency, low power consumption, low clock jitter, good power supply rejection ratio, low voltage ripple on the power supply, low charge injection in the substrate and small area.